This invention relates in general to a hitching system for coupling vehicles and, in particular, to a hitching system which may be selectively utilized to push or pull a vehicle.
More specifically, this invention relates to a hitching system particularly adapted for use with tandem loading earth moving vehicles and adapted to cushion the impact incurred upon pushing or pulling the loading vehicle.
During the excavating of material, such as encountered in land leveling and various types of construction wherein earth moving vehicles are utilized to cut earth from a borrow site and move it to a fill site, scraper type vehicles which include a scoop or bucket, known as a bowl, are employed to cut the earth from the borrow site and carry it to the fill site for unloading. Maximum power requirements are needed during the filling or cutting portion of the operation when the scraper bowl is cutting the earth from the borrow site and loading the fill into the bowls to be conveyed to the fill site. In difficult soil conditions, the vehicle tires frequently slip and spin when the bowl is engaged in the filling operation, thereby dissipating power. Therefore, it has been common practice to utilize an assist vehicle, either a crawler tractor or a second scraper, at the borrow site to push against the rear or to pull at the front of the loading vehicle to supplement the power required for the loading or filling operation.
During tandem loading operation when a crawler tractor is utilized, such operation is wasteful of both equipment and manpower due to the fact that the crawler equipment must be on standby except during that period of time in which it is utilized to assist the scraper in the loading or cutting operation. Therefore, to eliminate the necessity of having to maintain a crawler type tractor to assist in the loading operations, scraper vehicles are used in tandem relationship. A pair of scrapers are coupled together such that a following scraper pushes against the rear of the leading vehicle in order to supplement the tractive effort of the forward vehicle during the cutting or loading operation. During such operation, the assisting or following scraper normally has its bowl clear of the ground and is used only to supplement the tractive effort of the forward or loading vehicle. When the forward vehicle has been loaded, the bowl is raised clear of the ground and the forward vehicle assists in loading the following vehicle in a similar operation.
To avoid requiring that the forward or loaded vehicle reverse position to push against what heretofore was the following vehicle, various hitches or couplings have been designed for both pushing and pulling operations. Upon the loading of the forward vehicle with the assistance of the following pushing vehicle, a hitch is utilized to engage a suitable hook on the rear portion of the forward vehicle to pull the following vehicle during loading. While various hitch assemblies which alternatively function as a push-type hitch and a pull-type hitch have been utilized, such devices have not proven effective over uneven terrain when one of the coupled vehicles may be at a substantially different elevation or at an angle relative to the other resulting in frequent disconnection. In addition, impact between the vehicles upon engagement or during tandem loading frequently causes damage to the vehicles and, therefore, in order to minimize such damage the engagement of the vehicles is frequently extremely time consuming.